Local environment of W and Mo atoms in CaW_1-xMo_xO₄ (x = 0.12) solid solution studied by X-ray structural analyzes

The local environment of W and Mo atoms in CaW_1-xMo_xO₄ (x = 0.12) solid solution (mixed crystal) scintillator crystal was analyzed by X-ray diffraction (XD), extended X-ray absorption fine structure (EXAFS), and X-ray fluorescence holography (XFH). The XD analysis revealed that W and Mo atoms occupy the same crystallographic site. The analyzes of XFH and EXAFS exhibited that the local environment of Mo atoms is different from that of W atoms. Atomic images of neighbor atoms around the Mo and W atoms were reconstructed using their positional fluctuations. The positional fluctuation of the W atoms was apparently larger than that of Mo atoms. This feature explained the absence of the peak due to next nearest neighbor O atoms around W atoms in the Fourier transfer magnitudes for the W-L ₃ edge EXAFS spectrum. It is, therefore, most likely that the different positional fluctuations of the Mo and W atoms are responsible for different atomic images of neighbor atoms between them.